In the early 1990s, ethanol and methanol blends of alcohol gasoline were developed to reduce the amount of hydrocarbons spilled into the air from incomplete combustion during burning of gasoline in automobiles and light trucks. These fuels were found to be corrosive to certain iron, copper, silver, and aluminum bearing alloys contained in fuel pumps which were positioned within the fuel tank. As a result of this corrosive action, automotive engineers have shifted to the use of plastics, carbons, and polymers for fuel pump components due to their resistance to corrosion from alcohol fuels.
More recently, there is a movement toward placing electric in-tank fuel pumps in the fuel tank for transport of diesel fuel to the engine rather than using vacuum created by an engine driven fuel pump. During the development of the initial in-tank or in-line fuel pumps, it was discovered that diesel fuel was corrosive to DC carbon brushes and experimentation has led to the use of special carbon-laden brushes and carbon-covered commutations.
Vehicle design trends toward lower profile overall body designs have resulted in very shallow fuel tanks. This design requirement causes difficulty in packaging of existing fuel pumps in shallow tanks. Current fuel pumps typically have a 38 millimeter diameter and are 110 to 120 millimeters in axial length. Accordingly, difficulties arise in packaging such a long pump in a fuel tank which may only be 120 millimeters deep.
Other design factors leading to the development of the present invention include: 1) the cost of machined aluminum pump chamber bodies and covers; 2) the cost of carbon-covered commutators and longer life carbon alloy brushes; 3) the use of round commutators versus flat, placing the brushes perpendicular to the pump axis to reduce pump axial length; and 4) increased pump-motor diameter to increase motor efficiency and lower system current, while reducing pump axial length.
Accordingly, it is desirable to provide an in-tank or in-line fuel pump with substantially reduced axial length which takes in consideration the above-referenced design factors.